The Relative Variational Principle by Ledrappier and Walters: A survey

Ledrappier and Walters’s article “A Relativised Variational Principle for Continuous Transformations”, J. Lond. Math. Soc. (2) 16 (1977), no.3, 568-576) is a landmark in the development of Thermodynamic Formalism. This survey, aimed at newcomers to the field and experts in adjacent fields discusses the background, the Ledrappier-Walters article and some subsequent developments in the field.